Feedback of channel quality information

ABSTRACT

Methods and apparatus are presented for improving the feedback of channel information to a serving base station, which allows a reduction in the reverse link load while allowing the base station to improve the forward link data throughput. Over a channel quality indicator channel, a carrier-to-interference (C/I) symbol is transmitted over multiple slots at a reduced rate, which increases the likelihood that the base station can decode said symbol. The reduced rate mode can be selectively triggered by a high velocity condition or other unfavorable channel condition. The C/I symbol is used to determine transmission formats, power levels, and data rates of forward link transmissions.

BACKGROUND

1. Field

The present invention relates generally to communications, and morespecifically, to improving the feedback of channel information, whichcan be used to improve the scheduling and rate control of traffic over awireless communication system.

2. Background

The field of wireless communications has many applications including,e.g., cordless telephones, paging, wireless local loops, personaldigital assistants (PDAs), Internet telephony, and satellitecommunication systems. A particularly important application is cellulartelephone systems for mobile subscribers. As used herein, the term“cellular” system encompasses both cellular and personal communicationservices (PCS) frequencies. Various over-the-air interfaces have beendeveloped for such cellular telephone systems including, e.g., frequencydivision multiple access (FDMA), time division multiple access (TDMA),and code division multiple access (CDMA). In connection therewith,various domestic and international standards have been establishedincluding, e.g., Advanced Mobile Phone Service (AMPS), Global System forMobile (GSM), and Interim Standard 95 (IS-95). IS-95 and itsderivatives, IS-95A, IS-95B, ANSI J-STD-008 (often referred tocollectively herein as IS-95), and proposed high-data-rate systems arepromulgated by the Telecommunication Industry Association (TIA) andother well known standards bodies.

Cellular telephone systems configured in accordance with the use of theIS-95 standard employ CDMA signal processing techniques to providehighly efficient and robust cellular telephone service. Exemplarycellular telephone systems configured substantially in accordance withthe use of the IS-95 standard are described in U.S. Pat. Nos. 5,103,459and 4,901,307, which are assigned to the assignee of the presentinvention and incorporated by reference herein. An exemplary systemutilizing CDMA techniques is the cdma2000 ITU-R Radio TransmissionTechnology (RTT) Candidate Submission (referred to herein as cdma2000),issued by the TIA. The standard for cdma2000 is given in the draftversions of IS-2000 and has been approved by the TIA and 3GPP2. AnotherCDMA standard is the W-CDMA standard, as embodied in 3^(rd) GenerationPartnership Project “3GPP”, Document Nos. 3G TS 25.211, 3G TS 25.212, 3GTS 25.213, and 3G TS 25.214.

The telecommunication standards cited above are examples of only some ofthe various communication systems that can be implemented. Some of thesevarious communication systems are configured so that remote stations cantransmit information regarding the quality of the transmission medium toa serving base station. This channel information can then be used by theserving base station to optimize the power levels, the transmissionformats, and the timing of forward link transmissions, and further, tocontrol the power levels of reverse link transmissions.

As used herein, “forward link” refers to the transmissions directed froma base station to a remote station and “reverse link” refers totransmissions directed from a remote station to a base station. Theforward link and the reverse link are uncorrelated, meaning thatobservations of one do not facilitate the prediction of the other.However, for stationary and slow-moving remote stations, thecharacteristics of the forward link transmission path will be observedto be similar to the characteristics of the reverse link transmissionpath in a statistical sense.

Channel conditions of received forward link transmissions, such as thecarrier-to-interference (C/I) ratio, can be observed by a remotestation, which reports such information to a serving base station. Thebase station then uses this knowledge to schedule transmissions to theremote station selectively. For example, if the remote station reportsthe presence of a deep fade, the base station would refrain fromscheduling a transmission until the fading condition passes.Alternatively, the base station may decide to schedule a transmission,but at a high transmission power level in order to compensate for thefading condition. Alternatively, the base station may decide to alterthe data rate at which transmissions are sent, by transmitting data informats that can carry more information bits. For example, if thechannel conditions are bad, data can be transmitted in a transmissionformat with redundancies so that corrupted symbols are more likely to berecoverable. Hence, the data throughput is lower than if a transmissionformat without redundancies were used instead.

The base station can also use this channel information to balance thepower levels of all the remote stations within operating range, so thatreverse link transmissions arrive at the same power level. In CDMA-basedsystems, channelization between remote stations is produced by the useof pseudorandom codes, which allows a system to overlay multiple signalson the same frequency. Hence, reverse link power control is an essentialoperation of CDMA-based systems because excess transmission poweremitted from one remote station could “drown out” transmissions of itsneighbors.

In communication systems that use feedback mechanisms to determine thequality of the transmission media, channel conditions are continuouslyconveyed on the reverse link. A remote station monitors the channelquality of the forward link and feeds it back to the base station viathe Reverse Channel Quality Indicator Channel (R-CQICH). Thetransmission of a channel quality value on the R-CQICH is carried out inevery slot of the R-CQICH. For slow moving or stationary remotestations, the transmission of a channel quality value on each slotallows the base station to accurately predict the state of the forwardlink. However, when a remote station is traveling at a high velocity,the condition of the reverse link worsens so that the base stationcannot accurately decode the received channel quality values within adesignated frame error rate. Moreover, the high velocity causes fastfading conditions that the base station cannot accurately estimate usingoutdated channel quality values.

SUMMARY

Methods and apparatus are presented herein to address the problemsstated above. In one aspect, a channel quality feedback message isspread and/or repeated over multiple slots of a CQICH frame. In thisembodiment, the reception of the channel quality feedback becomesreliable because of the time diversity over the multiple slots. Theevents that trigger the repetition of channel quality feedback can be asfollows:

1. The base station detects that the channel quality feedback is notreliable and signals the mobile station to repeat the same channelquality feedback over multiple slots, or

2. The remote station can detect that its velocity is too high. Theremote station can either signal the base station that the channelquality feedback will be transmitted over multiple slots, as describedabove, or the remote station sends a request to the base station forsending the channel quality feedback message over multiple slots. Uponreceipt of an approval from the base station, the remote station startsthe channel quality feedback in the above fashion.

The repetition factors can be carried over the related signalingmessage, or the repetition factors can be predetermined as systemparameters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a wireless communication network.

FIG. 2A and FIG. 2B are timelines that describe the interactions betweenthe re-synch subchannel and the differential feedback subchannel.

FIG. 3 is a functional block diagram of a remote station incommunication with a base station.

FIG. 4 is a block diagram of channel elements for generating the channelquality feedback channel (CQICH).

DETAILED DESCRIPTION

As illustrated in FIG. 1, a wireless communication network 10 maygenerally includes a plurality of mobile stations (also called remotestations or subscriber units or user equipment) 12A–12D, a plurality ofbase stations (also called base station transceivers (BTSs) or Node B)14A–14C, a base station controller (BSC) (also called radio networkcontroller or packet control function 16), a mobile switching center(MSC) or switch 18, a packet data serving node (PDSN) or internetworkingfunction (IWF) 20, a public switched telephone network (PSTN) 22(typically a telephone company), and an Internet Protocol (IP) network24 (typically the Internet). For purposes of simplicity, four mobilestations 12A–12D, three base stations 14A–14C, one BSC 16, one MSC 18,and one PDSN 20 are shown. It would be understood by those skilled inthe art that there could be more or less number of mobile stations 12,base stations 14, BSCs 16, MSCs 18, and PDSNs 20.

In one embodiment the wireless communication network 10 is a packet dataservices network. The mobile stations 12A–12D may be any of a number ofdifferent types of wireless communication device such as a portablephone, a cellular telephone that is connected to a laptop computerrunning IP-based, Web-browser applications, a cellular telephone withassociated hands-free car kits, a personal data assistant (PDA) runningIP-based, Web-browser applications, a wireless communication moduleincorporated into a portable computer, or a fixed location communicationmodule such as might be found in a wireless local loop or meter readingsystem. In the most general embodiment, mobile stations may be any typeof communication unit.

The mobile stations 12A–12D may advantageously be configured to performone or more wireless packet data protocols such as described in, forexample, the EIA/TIA/IS-707 standard. In a particular embodiment, themobile stations 12A–12D generate IP packets destined for the IP network24 and encapsulate the IP packets into frames using a point-to-pointprotocol (PPP).

In one embodiment the IP network 24 is coupled to the PDSN 20, the PDSN20 is coupled to the MSC 18, the MSC 18 is coupled to the BSC 16 and thePSTN 22, and the BSC 16 is coupled to the base stations 14A–14C viawirelines configured for transmission of voice and/or data packets inaccordance with any of several known protocols including, e.g., E1, T1,Asynchronous Transfer Mode (ATM), LP, PPP, Frame Relay, HDSL, ADSL, orxDSL. In an alternate embodiment, the BSC 16 can be coupled directly tothe PDSN 20.

During typical operation of the wireless communication network 10, thebase stations 14A–14C receive and demodulate sets of reverse signalsfrom various mobile stations 12A–12D engaged in telephone calls, Webbrowsing, or other data communications. Each reverse signal received bya given base station 14A–14C is processed within that base station14A–14C. Each base station 14A–14C may communicate with a plurality ofmobile stations 12A–12D by modulating and transmitting sets of forwardsignals to the mobile stations 12A–12D. For example, as shown in FIG. 1,the base station 14A communicates with first and second mobile stations12A, 12B simultaneously, and the base station 14C communicates withthird and fourth mobile stations 12C, 12D simultaneously. The resultingpackets are forwarded to the BSC 16, which provides call resourceallocation and mobility management functionality including theorchestration of soft handoffs of a call for a particular mobile station12A–12D from one base station 14A–14C to another base station 14A–14C.For example, a mobile station 12C is communicating with two basestations 14B, 14C simultaneously. Eventually, when the mobile station12C moves far enough away from one of the base stations 14C, the callwill be handed off to the other base station 14B.

If the transmission is a conventional telephone call, the BSC 16 willroute the received data to the MSC 18, which provides additional routingservices for interface with the PSTN 22. If the transmission is apacket-based transmission such as a data call destined for the IPnetwork 24, the MSC 18 will route the data packets to the PDSN 20, whichwill send the packets to the IP network 24. Alternatively, the BSC 16will route the packets directly to the PDSN 20, which sends the packetsto the IP network 24.

In some communication systems, packets carrying data traffic are dividedinto subpackets, which occupy slots of a transmission channel. Forillustrative ease only, the nomenclature of a cdma2000 system is usedhereafter. Such use is not intended to limit the implementation of theembodiments herein to cdma2000 systems. Implementations in othersystems, such as, e.g., WCDMA, can be accomplished without affecting thescope of the embodiments described herein.

The forward link from the base station to a remote station operatingwithin the range of the base station can comprise a plurality ofchannels. Some of the channels of the forward link can include, but arenot limited to a pilot channel, synchronization channel, paging channel,quick paging channel, broadcast channel, power control channel,assignment channel, control channel, dedicated control channel, mediumaccess control (MAC) channel, fundamental channel, supplemental channel,supplemental code channel, and packet data channel. The reverse linkfrom a remote station to a base station also comprises a plurality ofchannels. Each channel carries different types of information to thetarget destination. Typically, voice traffic is carried on fundamentalchannels, and data traffic is carried on supplemental channels or packetdata channels. Supplemental channels are usually dedicated channels,while packet data channels usually carry signals that are designated fordifferent parties in a time and/or code-multiplexed manner.Alternatively, packet data channels are also described as sharedsupplemental channels. For the purposes of describing the embodimentsherein, the supplemental channels and the packet data channels aregenerically referred to as data traffic channels.

Voice traffic and data traffic are typically encoded, modulated, andspread before transmission on either the forward or reverse links. Theencoding, modulation, and spreading can be implemented in a variety offormats. In a CDMA system, the transmission format ultimately dependsupon the type of channel over which the voice traffic and data trafficare being transmitted and the condition of the channel, which can bedescribed in terms of fading and interference.

Predetermined transmit formats, which correspond to a combination ofvarious transmit parameters, can be used to simplify the choice oftransmission formats. In one embodiment, the transmission formatcorresponds to a combination of any or all of the following transmissionparameters: the modulation scheme used by the system, the number oforthogonal or quasi-orthogonal codes, an identification of theorthogonal or quasi-orthogonal codes, the data payload size in bits, theduration of the message frame, and/or details regarding the encodingscheme. Some examples of modulation schemes used within communicationsystems are the Quadrature Phase Shift Keying scheme (QPSK), 8-ary PhaseShift Keying scheme (8-PSK), and 16-ary Quadrature Amplitude Modulation(16-QAM). Some of the various encoding schemes that can be selectivelyimplemented are convolutional encoding schemes, which are implemented atvarious rates, or turbo coding, which comprises multiple encoding stepsseparated by interleaving steps.

Orthogonal and quasi-orthogonal codes, such as the Walsh code sequences,are used to channelize the information sent to each remote station. Inother words, Walsh code sequences are used on the forward link to allowthe system to overlay multiple users, each assigned one or severaldifferent orthogonal or quasi-orthogonal codes, on the same frequencyduring the same time duration.

A scheduling element in the base station is configured to control thetransmission format of each packet, the rate of each packet, and theslot times over which each packet is to be transmitted to a remotestation. The terminology “packet” is used to describe system traffic.Packets can be divided into subpackets, which occupy slots of atransmission channel. “Slot” is used to describe time duration of amessage frame. The use of such terminology is common in cdma2000systems, but the use of such terminology is not meant to limit theimplementation of the embodiments herein to cdma2000 systems.Implementation in other systems, such as, e.g. WCDMA, can beaccomplished without affecting the scope of the embodiments describedherein.

Scheduling is a vital component in attaining high data throughput in apacket-based system. In the cdma2000 system, the scheduling element(which is also referred to as a “scheduler” herein) controls the packingof payload into redundant and repetitious subpackets that can besoft-combined at a receiver, so that if a received subpacket iscorrupted, it can be combined with another corrupted subpacket todetermine the data payload within an acceptable frame error rate (FER).For example, if a remote station requests the transmission of data at76.8 kbps, but the base station knows that this transmission rate is notpossible at the requested time due to the condition of channel, thescheduler in the base station can control the packaging of the datapayload into multiple subpackets. The remote station will receivemultiple corrupted subpackets, but will still be likely to recover thedata payload by soft-combining the uncorrupted bits of the subpackets.Hence, the actual transmission rate of the bits can be different fromthe data throughput rate.

The scheduling element in the base station uses an open-loop algorithmto adjust the data rate and scheduling of forward link transmissions.The open-loop algorithm adjusts transmissions in accordance with thevarying channel conditions typically found in a wireless environment. Ingeneral, a remote station measures the quality of the forward linkchannel and transmits such information to the base station. The basestation uses the received channel conditions to predict the mostefficient transmission format, rate, power level and timing of the nextpacket transmission. In the cdma2000 1xEV-DV system, the remote stationscan use a channel quality feedback channel (CQICH) to convey channelquality measurements of the best serving sector to the base station. Thechannel quality may be measured in terms of a carrier-in-interference(C/I) ratio and is based upon received forward link signals. The C/Ivalue is mapped onto a five-bit channel quality indicator (CQI) symbol,wherein the fifth bit is reserved. Hence, the C/I value can have one ofsixteen quantization values.

Since the remote station is not prescient, the remote station transmitsthe C/I values continuously, so that the base station is aware of thechannel conditions if ever any packets need to be transmitted on theforward link to that remote station. The continuous transmission of4-bit C/I values consumes the battery life of the remote station byoccupying hardware and software resources in the remote station.

In addition to the problems of battery life and reverse link loading,there is also a problem of latency. Due to propagation and processingdelays, the base station is scheduling transmissions using outdatedinformation. If the typical propagation delay is 2.5 ms in duration,which corresponds to a 2-slot delay in systems with 1.25 ms slots, thenthe base station may be reacting to a situation that no longer exists,or may fail to react in a timely manner to a new situation.

For the above reasons, the communication network requires a mechanism toconvey information to the base station that allows the base station toquickly reschedule transmissions due to sudden changes in the channelenvironment. In addition, the aforementioned mechanism should reduce thedrain on battery life of the remote station and the load on the reverselink.

The embodiments described herein are directed to improving the feedbackmechanism for conveying channel information, such as thecarrier-to-interference (C/I) ratio, from the remote station to the basestation while reducing the load of the reverse link. By improving thefeedback mechanism, the embodiments improve the ability of a basestation to schedule transmissions and the data rates of thetransmissions in accordance with actual channel conditions. In oneembodiment, the base station uses the full C/I value that is associatedwith a first transmission channel in order to determine the scheduling,data rates, and transmission formats of traffic on a second transmissionchannel. For example, the channel conditions of the pilot can be used todetermine the conditions of a traffic channel.

In a general description of the embodiments, full C/I values aretransmitted on the CQI channel in a reduced rate mode, wherein operationin the reduced rate mode is triggered by detection of unfavorablechannel conditions or by detection of a high velocity condition.Detection procedures can be implemented at either a base station or aremote station.

Operating the CQICH in a Reduced Rate Mode

The values sent on the CQI channel are determined based on the forwardlink C/I measurements. In one embodiment, the C/I measurements aretransmitted at a reduced rate mode. In a reduced rate mode, a full C/Ivalue is spread over at least two slots of an N-slot CQICH frame. Forexample, the full C/I value may be transmitted at a reduced rate over 2,4, 8, or 16 slots of a 16-slot CQICH frame.

The remote station should transmit the full C/I value at the reducedrate when the reverse link is suffering from unfavorable channelconditions. In one embodiment, the base station determines unfavorablereverse link channel conditions and transmits a control signal to theremote station, wherein the control signal informs the remote station asto whether the CQI channel should operate at a reduced rate or not.Alternatively, the remote station can be programmed to make thisdetermination independently. In one embodiment, the remote stationpredicts that the conditions will become unfavorable due to highvelocity, i.e., the remote station determines that it is movingapproximately 30 km/h or faster.

In one implementation of the embodiment, a C/I value is transmitted onceover M slots of a N-slot frame. FIG. 2A illustrates this implementation.In another embodiment, a C/I value is transmitted repetitiously every Kslots of a N-slot frame. FIG. 2B is a timeline illustrating thisimplementation. In yet another embodiment, a full C/I value istransmitted over M slots, and repeated t times, such that t×M<N, i.e.,some of the slots of the CQI frame are not used for transmissions.

In another implementation, the full C/I value can be sent at unscheduledslots, whenever the remote station determines that the C/I estimate keptat the base station is out of synchronization. This embodiment requiresthat the base station is continuously monitoring the CQI channel todetermine whether an unscheduled full C/I value symbol is present ornot.

Triggering the CQI Channel Reduced Rate Mode from a Base Station

A scheduling element in a base station can be configured to interpretchannel information received on the CQI channel, wherein the channelinformation is used to make transmission decisions that account for thestate of the channel. The scheduling element can comprise a processingelement coupled to a memory element, and is communicatively coupled tothe receiving subsystem and the transmission subsystem of the basestation.

FIG. 3 is a block diagram of some of the functional components of a basestation with a scheduling element. A remote station 300 transmits on thereverse link to a base station 310. At a receiving subsystem 312, thereceived transmissions are de-spread, demodulated and decoded. Ascheduler 314 receives a decoded C/I value and orchestrates theappropriate transmission formats, power levels, and data rates oftransmissions from the transmission subsystem 316 on the forward link.

At the remote station 300, a receiving subsystem 302 receives theforward link transmission and determines the forward link channelcharacteristics. A transmission subsystem 306, in which the channelelements described by FIG. 4 is located, transmits such forward linkchannel characteristics to the base station 310.

In the embodiments described herein, the scheduling element 314 can beprogrammed to interpret the channel information received on the CQIchannel. In one embodiment, the base station can determine the energylevels of the symbols received on the CQI channel, compare the energylevels to a predetermined threshold amount, and then determine that theremote station should be transmitting the C/I values on the CQI channelin a reduced rate mode. The energy levels can be determined inaccordance with a number of methods. One quick, computationally lightmethod is the examination of the CQI bits that have been sent on the CQIchannel. Knowledge of the cumulative sum of the CQI bits can be used bythe base station (or the remote station) to determine the average powerof the received signals. In another method, the CQI decoder in the basestation can be configured to determine that the received bits do notclearly correspond to a valid codeword hypothesis, indicating thepotential presence of errors, and to report the potential for errors (orthe erasures resulting from said errors) to the scheduler. In oneembodiment the decoder consists in a correlation decoder, therebycorrelating the received signal with all possible codewords. The decodercompares the magnitude of the output of the strongest correlation C₁ tothe magnitude of the output of the second strongest correlation C₂, anddetermines that the received CQI signal does not clearly correspond to avalid codeword if the value (C₁–C₂) is below a threshold T_(diff), or ifC₁ is below a secondary threshold T₀.

Initiating the Reduced Rate Mode by a Remote Station

The remote station can also make a determination as to whether symbolstransmitted on the CQI channel should be transmitted at a reduced rateor not. In one embodiment, the remote station transmits a message to aserving base station that CQI channel transmissions will be at adesignated reduced rate. Alternatively, in another embodiment, theremote station transmits a request message to the serving base stationfor reduced rate operation and waits for the serving base station tosend a control message that allows such operation.

One of the methods for determining whether the symbols on the CQIchannel should be transmitted at a reduced rate is the use of velocityinformation. A general observation is that a remote station traveling athigh velocity will experience unfavorable channel conditions. Hence, inone embodiment, a processing element and a memory element can beconfigured to operate with other components of the remote station todetermine the velocity of the remote station, and then selectivelyimplement the reduced rate mode in accordance with the velocity. Forexample, at a high velocity of 30 km/h or greater, the transmissions onthe CQI channel will be sent at a reduced rate.

In another aspect of the embodiment, the velocity of the remote stationcan be determined through Doppler frequency estimation, which isproportional to the velocity of the remote station. Doppler estimationcan also be performed using knowledge of the transmitted power controlbits, at either the remote station or the base station.

The embodiments described above serve the practical purpose of allowingthe base station to more closely model the event of a fast fade, whichcan occur when a remote station is traveling at high velocities.Rayleigh fading, also known as multipath interference, occurs whenmultiple copies of the same signal arrive at the receiver in adestructive manner. Substantial multipath interference can occur toproduce flat fading of the entire frequency bandwidth. If the remotestation is travelling in a rapidly changing environment, deep fadescould occur at scheduled transmission times. When such a circumstanceoccurs, the base station requires channel information that allows it toreschedule transmissions quickly and accurately. At the reduced ratemode, the base station receives a reduced rate C/I value over more thanone slot, but the base station can still compensate for the fade beforethe C/I value is fully received over the multiple slots, if the basestation can partially decode the portion of the symbol that has alreadybeen received.

The use of reduced rate modes as described above allows the base stationto react to the changing environment in which the remote station isoperating.

FIG. 4 is a block diagram of channel elements that can implement theembodiments described above in a cdma2000 1xEV-DV system. C/I ratiovalues 401 are input into an encoder 402 at rate R=4/12 so that 12binary symbols are generated for each slot. The 12 binary symbols arespread with a Walsh code generated by a covering element 412. Coveringelement 412 selects one of six allowed spreading Walsh sequences basedon cover symbols 410 to indicate the index of the serving base station.The output of the covering element 412 and the encoder 402 are combinedby an adder 404 to form 96 binary symbols per slot. The output from theadder 404 is mapped in a mapping element 406 and then spread by a Walshspreading element 408 to generate the CQI channel 400.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans may implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. An apparatus for controlling the operation of a quality feedbackchannel in a wireless communication system, comprising: acomputer-readable memory element; and a processing element configured toexecute a set of computer-executable instructions stored on thecomputer-readable memory element, the set of said instructions for:determining a channel quality value associated with a transmissionchannel; determining a condition of the transmission channel; if thetransmission channel condition is favorable, then transmitting thechannel quality value over one slot of the channel quality feedbackchannel, wherein the condition of the transmission channel is determinedto be favorable by comparing energy levels of symbols received on thetransmission channel to a predetermined threshold amount; if the channelcondition is not favorable, then transmitting the channel quality valueover a plurality of slots of the channel quality feedback channel; anddetermining a transmission rate of the channel quality value over thefeedback channel based on the condition of the transmission channel. 2.The apparatus of claim 1, wherein the condition of the transmissionchannel is based upon a velocity estimate, wherein the velocity estimateis determined by a Doppler frequency estimation method.
 3. The apparatusof claim 1, wherein the condition of the transmission channel is basedupon a power level estimate.
 4. The apparatus of claim 1, wherein thecondition of the transmission channel is based upon whether a fast fadeoccurs in the transmission channel.
 5. A method for improving thereception of a channel quality value, comprising: determining whetherthe condition of a transmission channel is favorable; if the conditionof the transmission channel is favorable, then transmitting the channelquality value over one slot of a feedback channel, wherein the conditionof the transmission channel is determined to be favorable by comparingenergy levels of symbols received on the transmission channel to apredetermined threshold amount; if the condition of the transmissionchannel is unfavorable, then transmitting the channel quality value overmore than one slot of the feedback channel; and determining atransmission rate of the channel quality value over the feedback channelbased on the condition of the transmission channel.
 6. The method ofclaim 5, wherein transmitting the channel quality value over more thanone slot of the feedback channel further comprises: repeating thechannel quality value over a frame of the feedback channel.
 7. Themethod of claim 5, wherein the channel condition is unfavorable if afirst station and a second station travel at a high velocity in relationto each other, wherein the first station originates the feedback channeland the second station originates the transmission channel.
 8. A methodfor improving the reception of a channel quality value at a basestation, comprising: determining whether the condition of a feedbackchannel from a remote station is favorable, wherein the condition of thefeedback channel is determined to be favorable by comparing energylevels of symbols received on the feedback channel to a predeterminedthreshold amount; if the condition of the channel is unfavorable, thentransmitting a control signal to the remote station, wherein the controlsignal triggers a reduced rate mode for transmitting the channel qualityvalue over a feedback channel from the remote station; if the conditionof the channel is favorable, then allowing the remote station to controlthe transmission of the channel quality value over the feedback channel;and determining a transmission rate of the channel quality value overthe feedback channel based on the condition of the transmission channel.9. An apparatus for improving the reception of a channel quality valueat a base station, comprising: means for determining whether thecondition of a feedback channel from a remote station is favorable,wherein the condition of the feedback channel is determined to befavorable by comparing energy levels of symbols received on the feedbackchannel to a predetermined threshold amount; means for transmitting acontrol signal to the remote station if the condition of the channel isunfavorable, wherein the control signal triggers a reduced rate mode fortransmitting the channel quality value over a feedback channel from theremote station; and if the condition of the channel is favorable, thenallowing the remote station to control the transmission of the channelquality value over the feedback channel; and means for determining atransmission rate of the channel quality value over the feedback channelbased on the condition of the transmission channel.